1. Field of the Invention
The present invention relates to a device for electrical connection between a rotor and a stator. More particularly, it relates to an electrical connecting device between a steering wheel (handle) and a steering column in a steering apparatus for a vehicle.
2. Description of the Related Art
With the recent progress of automotive electronics, the automotive steering wheel has been provided with a variety of switches for electronic controls, which are required to be connected to various elements on the steering column's side through electrical wiring. Since the automotive steering wheel is adapted so as to rotate in both clockwise and counter-clockwise directions at plural revolutions, there is generally used an electrical connecting device between the steering wheel and the steering column, in which a flexible flat cable (FFC) having a plurality of lead wires (or conductors) is whirled between a rotor fixed to a handle shaft and a housing fixed on the steering column's side, in spiral or "halfway-reversed" spiral condition.
As the conventional electrical connecting device of halfway-reversed type, there is known an electrical connecting device disclosed in Japanese Patent Publication No. 8-78125. FIGS. 1 to 4 show the structure of the electrical connecting device. In the device, a housing 1 consists of an under cover 1a and an upper cover 1b between which a rotor 2 is rotatably arranged. The rotor 2 comprises a lower rotor body 2a, an intermediate rotor body 2b and an upper rotor body 2c which are all integrated into one body through some screws 3. The resultant rotor 2 is fixed to a not-shown shaft on a steering wheel's side, while the housing 1 is fixed to a not-shown member on a steering column's side.
A ring-shaped cable accommodating chamber (annular space) 4 is defined between the housing 1 and the rotor 2. The cable accommodating chamber 4 has an inner peripheral face 4a and an inside lower face both constituted by the rotor 2. While, an outer peripheral face 4b, an upper face 4c and an outside lower face of the chamber 4 are constituted by the housing 1. A flexible flat cable (FFC) 5 is accommodated in the cable accommodating chamber 4. The flexible flat cable 5 has one end connected to a connector 6 on the rotor's side and the other end connected to a connector 7 on the housing's side. The end portion of the flexible flat cable 5 is wound around the inner peripheral face 4a in one winding direction. While, the other end portion of the cable 5 is wound along the outer peripheral face 4b in another direction opposite to the above winding direction. Thus, the cable's winding direction on the inner peripheral face's (4a) side is reversed to the cable's winding direction on the outer peripheral face's (4b) side, forming a turn-over part 5a as a boundary.
In the cable accommodating chamber 4, there are provided a carrier 9 for rotatably supporting a number of guide rollers 8 through pins 9a, and a movable internal gear 10. The carrier 9 is arranged between a winding part 5b of the cable 5 on the side of an inner peripheral face 4a and another winding part 5c on the side of an outer peripheral face 4b. The above turn-over part 5a of the cable 5 is disposed about the designated guide roller 8 on the carrier 9. Below the carrier 9, a planetary gear 11 is rotatably supported by the carrier 9. The planetary gear 11 meshes with both outer teeth 12 formed on the intermediate rotor body 2b and inner teeth 13 formed on the internal gear 10.
As shown in FIG. 4, the upper cover 1b is provided, on the upper face 4c of the chamber 4, with an inside projection 14a and an outside projection 14b which both project downward on the inner peripheral side and the outer peripheral side of the chamber 4, respectively. In the circumferential direction of the upper cover 1b, the inside projection 14a is formed on a level with the outside projection 14b.
In the above-mentioned arrangement, when the rotor 2 rotates in the clockwise direction (i.e. the direction of a of FIG. 2), then the winding part 5b about the inner peripheral face 4a is continuously fed out to be the turn-over part 5a about the designated guide roller 8 on the carrier 9 and finally rolled into the outer peripheral face 4b.
With this feeding and rolling operation of the flexible flat cable 5, the turn-over part 5a of the cable 5 gradually moves in the clockwise direction. During this movement, the planetary gear 11 is rotated by the rotation of the rotor 2. Further, due to the transmission of rotating force, the carrier 9 is also moved to the clockwise direction in the chamber 4. In this way, the electrical connecting device can perform the cable feeding and rolling operations while the flexible flat cable 5 is subjected to no external force from the carrier 9.
On the contrary, when the rotor 2 rotates in the counter-clockwise direction (i.e. the direction of b of FIG. 2), then the winding part 5c about the outer peripheral face 4b is continuously fed out to be the turn-over part 5a about the designated guide roller 8 on the carrier 9 and finally rolled into the inner peripheral face 4a. The carrier 9 is moved to the counter-clockwise direction in the chamber 4 for the above-mentioned reason. In this way, also in this case, the electrical connecting device can perform the cable feeding and rolling operations while the flexible flat cable 5 is subjected to no external force from the carrier 9.
Meanwhile, if the turn-over part 5a of the flexible flat cable 5 slides on the upper face 4c of the chamber 4 in process of clockwise or counter-clockwise movement of the part 5a, then a great noise may be produced since the turn-over part 5a is arranged relatively free in vibration. It should be understood that, in the conventional device, the provision of the projections 14a and 14b on the upper face 4c is based on such an apprehension of noise.
That is, even if the upward force is applied on the flexible flat cable 5, the turn-over part 5a of the flexible flat cable 5 is prevented from the contact with the upper face 4c, owing to the initiative contact of the winding parts 5b and 5c with the projections 14a and 14b.
However, it is also noted that, in the conventional electrical connecting device between the steering wheel and the steering column, the winding part 5b of the cable 5 (on the side of the inner peripheral face 4a) rotates together with the rotation of the rotor 2. Consequently, the sliding of the top edge of the cable part 5b on the inside projection 14a would cause the occurrence of noise.